Corn and many other crops are normally grown in parallel rows. Controlling weeds that grow between the rows is a serious problem. One method employs chemical herbicides, but such herbicides can cause environmental or chemical resistance problems and are expensive. An alternative to chemical control of weeds is to use mechanical means to cultivate between the rows.
In one type of row crop planting, the ridge developed from the previous year's crop serves as the seedbed. During planting, approximately 1½ inches of soil are removed from the top and sides of the ridge. The soil, weeds and weed seed are then removed to the side of the ridge. The crop is then planted into this ridge with the hope that it has time to germinate and grow before new weeds can become established.
Accomplishing weed control at planting time requires tillage equipment that can be positioned and maintained on the top and center of the previous year's ridge. The natural tendency for the row cleaning mechanism is to shift sideways off the top of the ridge. A very high degree of lateral stability is required to maintain the row cleaning mechanism on the top and center of the ridge.
It is also important that a starter fertilizer be placed next to the seed. One current suggestion for optimum placement of starter fertilizer is two inches to the side and two inches below the seed. The proper placement of the fertilizer is important if maximizing early growth is to be achieved.
Weed control during the cultivation process depends upon the crop becoming established and attaining a height of approximately four inches before new weeds can get started. This growth depends upon precise planting and fertilizing. One cultivation procedure is a two step process achieved in one pass through the field. The tool carrier places the tillage tool very close on each side of the plants and removes any weeds that exist in that area. The soil and weeds are removed to the side and away from the plants. The second step requires a mechanism equipped with a crop shield that is typically two inches wide at the bottom and approximately three feet long. As the crop passes through the shield, soil is moved into the row to a depth of about 1½ inches. This soil covers any weeds that were missed in the first cultivation step.
Current row crop equipment comprises a tool carrier with a three-point hitch assembly behind the rear axle. A laterally extending tool bar connects to the hitch. Various planting and cultivating equipment are mounted to the tool bar and spaced apart to match the rows. The lift arms and control links between the tool bar and the tool carrier are not rigidly attached to the tool carrier. As the tool carrier moves along the rows, the tool bar tends to move laterally. Better weed control could be achieved if the planting and cultivating equipment could be more precisely controlled. One goal would be to achieve an accuracy of plus or minus one inch while operating at speeds of 4.5 to 6.0 miles per hour. Planting, fertilizing and cultivating with currently available implements at this level of accuracy is not possible.